It might not negatively affect the efficiency, but the reasoning is that if you have intakes on both sides of the firebox, then you could close off one intake or the other depending on which way the wind is blowing. My patio sized reverse flow only has one intake, it's in the door. I did it that way only because I didn't know any better at the time.
If you decide to go with one intake, then yes you would double the dimensions to have the same amount of area for the intake.
Just make sure the top of the intake is at or lower than the the fire grate so the air is drawn through the fire.
Learning generally boils down to "Repetition or the avoidance of pain", some people learn by doing, some by watching and some just have to pee on the electric fence.
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Thanks for the welcomes and the advice guys! Makes complete sense to keep them on either side now that I think about it. Leaves you with better fire control options depending on wind airflow direction like y'all mentioned. I mean that's how my ol cheapo verticle works.....guess there's a reason I have newbie under my name lol. Anyways been reading the forum for the last few hrs reading about other builds and everyone seems to be quick to help others out! Digging the vibe already time for late night coffee and more researching haha. Hopefully by the weekend ill gets some pics posted of .y progress.....thanks again guys